How to Convert From SHGC to Shading Coefficients

Solar heat gain coefficient (SHGC) is the total percentage of solar energy at a window opening that is either absorbed and reflected into a building or directly transmitted through the window. In hot climates, like Arizona, a low SHGC helps reduce energy costs.

In cold weather, windows that absorb the sun's heat reduce energy costs.

In cold climates, however, a higher SHGC helps reduce energy costs. SHGC replaces a measurement called shading coefficient (SC). You may find references to shading coefficient in the ratings of older windows or in older reference materials. The relationship between the two ratings systems is straightforward, and the coefficients can be converted with a simple formula.

1. Use the formula SHGC = SC*0.87 to convert between SHGC and SC. Enter the value that you have and solve algebraically to calculate the value that you don't have.

2. Multiply SHGC by 1.15 to convert the value from SHGC to SC. This conversion factor is the result of solving algebraically and is a simple, shorthand version of the formula. You can use this step in place of algebraic conversion.

3. Multiply SC by 0.87 to convert from SC to SHGC.

The Drip Cap

• Solar heat gain coefficient (SHGC) is the total percentage of solar energy at a window opening that is either absorbed and reflected into a building or directly transmitted through the window.
• The relationship between the two ratings systems is straightforward, and the coefficients can be converted with a simple formula.
• Multiply SHGC by 1.15 to convert the value from SHGC to SC.